Established mobile communication systems rely on an architecture having a core network and a radio access network. One such typical example is the GSM mobile communication network where the core network comprises at least one gateway mobile services switching center GMSC, mobile switching center MSC, home location register HLR, and visitor location registers VLR. The gateway mobile services switching center GMSC is connected to a plurality of mobile switching centers MSC. Usually, each mobile switching center MSC is connected to a visitor location register VLR. Different visitor location registers VLR are connected to a home location register HLR, which is also linked to the gateway mobile services switching center GMSC.
With respect to the radio access network, each mobile switching center MSC serves a plurality of base station controllers BSC being connected to a plurality of base transceiver stations BTS for link establishment to mobile stations MS roaming in the area covered by the mobile communication network.
While such an architecture for mobile communication systems is well suited to support circuit switched services, general packet radio service GPRS has been introduced by the European Telecommunication Standards Institute ETSI to also support packet switched services for roaming subscribers.
Contrary to the circuit switched mobile communication network, the packet switched GPRS network is adapted to offer connection to a standard data network using protocols such as TCP/IP. Heretofore, for the architecture of the packet switched mobile communication network new functional elements are introduced.
With GPRS mobile communication systems the intra operator structure consists of support nodes, i.e. the gateway GPRS support nodes GGSN and the serving GPRS support nodes SGSN. The main function of the gateway GPRS support node GGSN is the interaction with the external data network and the update of a location directory using routing information supplied by the serving GPRS support nodes SGSN for a roaming mobile subscriber.
While the circuit switched mobile communication network—e.g., according to GSM or UMTS—and the packet switched mobile communication network—e.g., the general packet radio service GPRS—logically are operated independent from each other, nevertheless, they use resources in common to a certain extent, in particular on the signaling level.
For exchange of signaling information the serving GPRS support node has direct access to the radio access network via the Gb interface for GSM and via the lu for UMTS. Further, for exchange of information between the serving GPRS support node and the mobile switching center MSC/visitor location register VLR there is established a Gs interface. Still further, interface Gr allows to exchange information between the serving GPRS support node and the home location register HLR.
While the architecture described so far works well when there is established a 1:n relationship between each mobile switching center MSC and related base station controllers BSC, the architectures outlined above are not suitable when each base station controller may be served by a plurality of mobile station centers MSC to increase network capacity and reliability, i.e. when a plurality of mobile station centers MCS are integrated into a pool of mobile station centers MSC.
Today, there is no satisfactory proposal for a simultaneous operation of packet switched mobile communication networks in combination with circuit switched mobile communication systems when a pool of mobile switching centers MSC is provided in the circuit switched mobile cellular communication system. The reason for this is that there is no solution to the problem of re-distributing subscribers between mobile switching centers MSC in a related pool when packet switched services are used, except waiting for the subscribers to turn off and on their mobile station or to move to a new location area in the circuit switched mobile communication system. Since this can take a long time, it severely reduces the benefits of a mobile switching center MSC pool.